1. Field of the Invention
The invention relates to a spinal dynamic stabilization device which is positioned between adjacent vertebrae, more particularly adjacent spinal process, for decompressing nerves through distracting narrowed spinal canal or foramen, relieving back pain. The invention also discloses methods and devices for redistribution of compression loads to minimize occurrence of bone fracture.
2. Description of the Related Art
In the U.S., the largest spine device and apparatus market in the world, it is estimated that over two million patients visit doctors every year because of lower back pain. Of those, about 40 percent have degenerative disc disease, DDD. The number of patients in the world with lower back pain is expected to increase due to the aging world population. According to a recent forecast, up till 2009, over 51 millions people in the US will be expected to solve their spine problems by surgical intervention, spinal fusion surgery, for example. Decompression and fusion surgery are current surgical standards for lower back pain treatment. In general, decompression surgeries, laminectomy and distectomy, for example, are adapted as primary surgical interventions to relieve pain for patients in relative early stage of disc degeneration. For patients suffered from more severe spinal instability, spinal fusion surgery is clinically applied as final and gold standard to stabilized spinal column by fusion of two spinal columns.
Laminectomy is the process wherein the laminar of a spine is partially or totally removed to decompress nerves, thus preserving spinal motion in patients during the early stages of a degenerative spine. However, tissue removal during decompression can lead to improper spine biomechanics which might further facilitate disc degeneration. In contrast to decompression surgery, fusion surgery is clinically chosen as final solutions to help patients stabilized their degenerative spine. However, fusion surgery are not recognized as best solutions for patients due to some concerns that include: (1) limited movement of adjacent vertebrae; (2) acceleration of adjacent level degeneration, wherein the mechanics of the spine changed after spinal columns are fused and motions on the adjacent segment of increases to compensate for the fused segment; and (3) incomplete fusion resulting in pseudoarthrosis and easy fracturing, wherein in the worst cases, the implant cage is required to be removed.
Thus, non-fusion surgical techniques have been disclosed. Generally, dynamic stabilization systems such as the interspinous process spacer and pedicle screw-based systems have been developed to assist in preserving motion for patients after surgery.
Meanwhile, with increased advances in the medical field, minimally invasive surgery has become a trend. Compared with traditional surgery, advantages of minimally invasive surgery include: smaller incisions; decreased blood loss during surgery; and decreased probability for complications. Additionally, the amount of time required for surgery and recovery time are considered to be shortened once device and instrument is well-designed.
U.S. Patent No. 20070161992 discloses a vertebrae implant device with a pair of pivoting S-shaped arms. The arms in a closed state are implanted into adjacent vertebrae. After implantation, the arms are expanded to maintain a height between the adjacent vertebrae. However, the device is applied by traditional surgery methods, thus, resulting incisions are relatively large.
U.S. Patent No. 20070032790 discloses a device treating stenosis with an insertion element and a sleeve. The insertion element comprises one end, and the sleeve comprises the other end. Before implantation, two arms in a closed state are disposed in the sleeve. After implantation, the arms are expanded.
U.S. Patent No. 20060008983 discloses a device made of PU. Before implantation, the device is not filled with fluid. After implantation, gas or liquid is filled into the device, and the device expands into an H-shape. However, studies show that the strength and the fixation efficiency of the device are unsatisfactory.
U.S. Patent No. 20070276372 discloses a surgery method and a device utilizing the same. An axle device with procedure ends is implanted into a body via skin. After implantation, one end is pushed toward one direction, and the other end is pushed toward the other end to stabilize the spine.
U.S. Patent No. 20070173832 discloses MIS-based surgery methods, wherein a device is expanded and implanted.
U.S. Patent No. 2006008983 discloses a spine stabilization device with a supporting portion. When the supporting portion is implanted in the vertebra, the arms are pushed from two sides or are rotated to expand.